Massachusetts Democrats, still humbled by their defeat in the 2010 US Senate special election, are launching unusually early campaign attacks on the Republican Party, particularly targeting Senate candidate ­Michael J. Sullivan for his conservative social positions.

Democratic Party leaders and gay rights activists have planned a press conference for Wednesday where they will highlight Sullivan’s opposition to same-sex marriage. The party will hold another event later in the week to attack the former US attorney, who is considered the early front-runner in a three-way GOP primary, for his opposition to banning assault weapons.

The preprimary election engage­ment with the GOP is atypical in Massachusetts politics, where Democrats tend to pay little attention to Republican primary candidates, their fights often overshadowed by the higher-profile battles on the Democratic side.

But Republican Scott Brown’s stunning defeat of Democrat Martha Coakley in the January 2010 special election to fill the seat left empty by the death of Edward M. ­Kennedy is seared in the party’s memory, a lingering political trauma that is prompting its leaders to develop an aggressive strategy in the second US ­Senate special election ever held in Massachusetts.

The state Democratic Party, which has not endorsed either US Representative Stephen F. Lynch or US Representative ­Edward J. Markey, said it is convinced that focusing exclusively on attacking Sullivan as the face of the GOP in Massachusetts will help insulate the party against another special election upset.

“We believe that by shining a light on Sullivan, who is widely recognized as the Republican front runner, we can show that the Republican Party is much like the national Republican Party, out of touch, driven by the Tea Party to take extreme positions, and on the wrong side of the issues for Massachusetts,’’ state Democratic Party chairman John W. Walsh said in a statement Tuesday.

But there is another angle to the Democrats’ strategy. By highlighting Sullivan’s socially conservative positions, they hope to energize the GOP primary electorate, propelling ­Sullivan to victory and thereby ensuring that the Democratic nominee will face the most conservative of the three Republican candidates in the June 25 election.

‘The Democrats’ attack on him buys him free name identification, which he otherwise would have to pay for.’

Rob Gray, a GOP political consultant, called the Democrats attempt to shape the ­Republican race “highly unusual.”

Sullivan “is already the front-runner; the biggest question is whether he can raise enough money,” Gray said. “That is the area where he is unproven. The Democrats’ ­attack on him buys him free name identification, which he otherwise would have to pay for.’’

Sullivan has firmly staked out conservative social positions in the GOP primary. He has said he is opposed to abortion rights and gay marriage. He also opposes a ban on ­assault weapons and high ­capacity ammunition clips. His two primary opponents, state Representative Daniel P. ­Winslow and Cohasset businessman Gabriel E. Gomez, support gay marriage and abortion rights, but do not favor a ban on assault weapons.

With his political connections and electoral experience as a former state representative and Plymouth district attorney, Sullivan starts off the race as the GOP favorite, observers believe. His strength was demonstrated in his ability to collect some 20,000 certified voter signatures in just two weeks, using only volunteers. His two rivals used paid signature-gathering firms and still did not equal the numbers Sullivan’s volunteers collected.

“Shame on the politicians who, for their own political gain, promote cultural and class divisions between our people in times like these. We need leaders who bring people together, not tear them apart for political gain,” Moore said.

Though national Democrats have thrown their support ­behind Markey, the state Democratic Party is not involving ­itself in the primary battle ­between Lynch and Markey. ­Instead, party leaders say they will focus exclusively on helping to shape the Republican race to help make certain that they get the nominee they feel they are best poised to beat.

Walsh would not comment further on the Democrats’ strategy. But a memo from state Democrats, obtained by the Globe, indicates that the Democrats are also focusing on engag­ing the grass-roots organization that developed around Elizabeth Warren’s Senate candidacy and President Obama’s reelection campaign. They created what experienced political observers say was the most effec­tive get-out-the-vote organization the state has seen.

The party is particularly trying to hold onto the enthusiasm that was displayed last year in black, Asian, and Latino ­enclaves in the state. Turnout among those groups increased 8 percent in 2012 over 2008, accord­ing to the memo.

The vote in those communities was dramatically lower in the 2010 special election, a drop that the party is working hard to avoid this time. Walsh has held over a half-dozen meetings with minority leaders and is raising $250,000 for voter outreach and turnout efforts.

The party is also concentrating on what its leaders call “new voters’’ — 170,000 registered Democrats who voted for the first time in 2012. Getting that bloc of voters to the polls for the June 25 general election is considered a major priority.